Router with quick tool replacement

Abstract: Router for carpentry including a vertical tubular post (2) which is supported on a base (1) and a hollow shaft (5) which is rotatably supported in the tubular post (2) and is connected, at its lower end, to rotational actuation elements (6); the router is characterized in that the top of the hollow shaft has a conical seat (13) for the coupling of the conical tang (14) of a tool supporting shaft (15); means are provided to retain the tang in the seat and to provide the rotary coupling between the hollow shaft and the tool supporting shaft; means are further provided to release the tang from the seat and to allow the removal of the tool supporting shaft.

Description: The present invention relates to a router for carpentry with quick tool replacement as per the preamble of claim 1. An example of such a router is disclosed in WO 81/02401A. In carpentry, particularly for the beadwork of panels, wooden tiles and the like, vertical milling machines (hereinafter simply termed "routers" for convenience in description) are known to include a milling tool coupled to the top of a vertical shaft that protrudes above a working surface on which the part to be machined is moved. In conventional routers, every time a new profile must be formed it is necessary to replace the old milling tool with a new one. This leads to the need to use tools having holes of the same diameter so that they can be fitted on the same shaft, and this sets limits to the structure of the tool. In other kinds of routers the tool is mounted on a replaceable shaft in order to obviate this drawback. Nonetheless, it is still necessary to remove the tool before accessing the shaft. Furthermore, it has been found that the means for fixing the shaft are difficult or at least awkward to access. The technical aim of the present invention is to provide a router that allows to overcome the shortcomings of those currently commercially available and in particular allows rapid tool mounting and removal operations and the use of tools having different internal diameters. This aim is achieved with a router for carpentry as in claim 1. Further characteristics and advantages of the router according to the present invention will become apparent from the following detailed description of a preferred embodiment, illustrated only by way of non-limitative example in the accompanying drawing, wherein: the only figure is a vertical sectional view of a router according to the new inventive concept. With reference to the above figure, the router comprises a plate 1 on which a tubular post 2 is fixed; said post rises vertically and a hollow shaft 5 is rotatably supported inside it by means of bearings 3 and 4. A pulley 6 is keyed on the portion of the hollow shaft 5 that lies below the plate 1 and is driven, by means of a belt which is not shown, by an electric motor mounted onto said plate. The pulley 6 is rigidly coupled to the hollow shaft 5 by means of rings 7 and 8 having a wedge-like cross-section and forced between the pulley and the hollow shaft by means of a ring 9. The upper bearing 4 is protected by a labyrinth seal formed by a first ring 10 which is fixed to the top of the post 2 and by a second ring 11 which is fixed to the top of the hollow shaft 5; the oppositely arranged surfaces of said rings 10 and 11 have concentric ridges and grooves that mutually interpenetrate. The hollow shaft 5 is axially crossed by a cylindrical cavity 12 which widens at its upper end so as to form a conical seat 13 that is flared upwardly. The complementarily tapered tang 14 of a tool supporting shaft 15 is adapted to engage the conical seat 13. The tang 14 is separated from the shaft 15 by a collar 16 having two diametrical notches 17 in which two respective tabs 18, extending axially from the top of the hollow shaft 5, engage to provide a rotational actuation coupling. According to a known method which accordingly is not described in detail, the tool is placed on the shaft 15 with the aid of spacer rings 19 and locked against the collar 16 by a bolt 20 which is axially screwed into the shaft 15 with the interposition of a washer 21 which, by means of teeth 22, provides a rotary coupling with the shaft 15, preventing the loosening of the bolt 20 when the shaft 15 stops and starts. A coaxial mushroom-like stem 23 is screwed to the lower end of the tang 14, and a collet-like element 24 of the type that expands cylindrically cooperates with said stem. The collet 24 is substantially constituted by sectors that oscillate on radial planes and the upper ends whereof are curved outwardly to engage an abutment constituted by an annular step 25 which is obtained from an expansion in the region of transition between the conical seat 13 and the cylindrical cavity 12 of the hollow shaft 5. The sectors of the collet furthermore have internal undercuts for the engagement of the head of the stem 23 and of a pin 26 which is fixed to the top of a stay bolt 27 which is guided in the cylindrical cavity 12. From the foregoing it is evident that when the stay bolt 27 is actuated downward, the collet 24, by abutting against the abutment 25, closes and engages the stem 23, thus forcing the tang 14 into the seat 13. The traction force applied by the stay bolt 27 is provided by a pack of springs 28 accommodated in a chamber 29 formed between the rod 27 and the hollow shaft 5 and more precisely by providing a reduction in the outer diameter of the bolt 27 and an expansion of the cylindrical cavity 12. The pack of springs 28 rests at the top against a ring 30 which is retained by radial screws 31 and at the bottom against a bush 32 which is screwed to the lower end of the bolt 27 and is centered on the hollow shaft 5 with the interposition of a sealing ring 33. A jack 34, fixed to the plate 1 by a support 35, is provided to actuate the stay bolt 27 in the direction that allows the collet 24 to open and thus allows to remove the tool supporting shaft 15. The jack 34 has the stem 36 coaxial to the hollow shaft 5 and comprises a collar 37 that forms, together with a flanged ring 38 fixed to the shaft 5 below the pulley 6, a chamber 39 which accommodates two sensors 40 and 41 for detecting the axial position of the bolt 27 and of the stem 36. A third sensor, not shown in the drawing, cooperates with the ring 38 to detect the rotation of the shaft 5. The coupling between the flanged ring 38 and the collar 37 is protected by a bell-shaped expansion 42 of the pulley 6. The described router is completed by a sleeve 43 which is supported in the base of the machine so as to allow to tilt the post 2 with respect to the vertical. The post 2 can furthermore be arranged along the sleeve 43 to determine the arrangement of the tool with respect to the working surface. As can be deduced from the above description, the fundamental prerogative of the machine according to the present invention resides in that a quick and safe system for tool replacement has been provided. Indeed, starting from the position in which the tool is mounted, as shown in the figure, by actuating the jack 34, by means of the stem 36 that acts against the stay bolt 27, first the collet 24 opens and then, as the stroke of the stay bolt 27 continues, the pin 26 abuts against the stem 23 and the tang 14 is expelled from the seat 13. Then, after inserting the tang of a new shaft with a new tool in the seat 13, by releasing the jack 34 the pack of springs 28 pulls the stay bolt 27 downward so that the collet 24, by abutting against the abutment 25, closes on the head of the stem 23 and retains the tang in the seat 13. According to a particularity of the invention, the stay bolt 27 and the stem 36 are axially crossed by respective channels 44 and 45 which are mutually connected by lifting the stem 36. A gasket 46 is conveniently arranged around the outlet of the channel 44 and forms a front seal between the opposite ends of the bolt 27 and of the stem 36. The channel 44 ends upward at the collet 24, and the channel 45, during tool replacement, is connected to a source of compressed air, so that when the stem 36 acts on the bolt 27 to expel the tang 14 from the seat 13, the compressed air supplied through the channels 44 and 45 keeps the conical coupling region clean, preventing the penetration of particles (shavings or dust) that might compromise the precision of this coupling. At the same time, the external venting of the air can be used to indicate the tool replacement step. The arrangement of the sensors 40 and 41 has proved itself advantageous. In particular, a mismatch between the sensor 40 and the bush 32 indicates the imperfect penetration of the tang 14 in the seat 13, whereas the sensor 41 stops the machine if the stem 36 is in raised position. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: A router for carpentry comprising: a tubular post (2) being supported on a base (1); a hollow shaft (5) which is rotatably supported in said tubular post (2) and is connected to rotational actuation elements, said hollow shaft (5) having, at an end thereof, a conical seat (13) for the coupling of the tapered tang (14) of a tool supporting shaft (15); means (23, 24, 27) for retaining said tang (14) in said seat (13); means (16,17,18) for providing the rotary coupling between said hollow shaft (5) and said tool supporting shaft (15); means (34) for releasing said tang (14) from said seat (13) to allow the removal of said tool supporting shaft (15); and a pin (26), fixed to an end of a stay bolt (27) which is guided in a cylindrical seat cavity (12) crossing said hollow shaft (5), adapted to abut on the free end of said tang (14) for its expulsion from said seat (13) following the release of the tang from said tang retaining means (23, 24, 27), characterized in that the tubular post (2) is vertical, whereby the hollow shaft (5) is connected to the rotational actuation elements at the lower end thereof and has the conical seat (13) at its top end and the pin (26) is fixed to the top end of the stay bolt (27), and in that it further comprises air supply channels (44, 45), which axially cross said stay bolt (27) and a stem (36) movable to abut on said stay bolt (27), said air channels (44, 45) being mutually connected by lifting the stem (36) for supplying compressed air at the conical seat (13), during expulsion of said tang (14), for external venting of the air which is indicative that a tool changing operation is in course, and so as to keep clean said seat (13), and Two sensors (40, 41) provided to detect the axial position of said stay bolt (27) and said stem (36) respectively whereby to indicate imperfect penetration of a newly inserted tool tang (14) in said seat (13). Router according to claim 1, characterized in that said means for retaining said tang in said seat comprises the stay bolt (27) which is slidingly accommodated in said hollow shaft (5) and is provided, at one end, with a collet (24), elastic traction means (28) being provided which move said bolt (27) from a position in which said collet is open, in order to receive a stem (23) of said tang (14), toward a position in which said collet (24) is closed to couple to said stem (23) and said elastic means (28) retain said tang (14) in said seat (13). Router according to claim 2, characterized in that said tool expelling means comprises a pin (26) which is fixed at the end of said stay bolt (27) where the collet (24) is provided, and in that said collet comprises undercuts for engagement with said pin (26). Router according to claim 2 or 3, characterized in that said elastic means are constituted by a pack of springs (28) which are accommodated in a chamber (29) formed between said hollow shaft (5) and said bolt (27) and abut, on one side, against a shoulder (30) of the hollow shaft (5) and, on the other side, against a shoulder (32) of the bolt (27). Router according to claim 2, 3 or 4 characterized in that said collet (24) is of the expansion type with sectors that close on the stem (23) of the tang (14) upon abutment against an abutment (25) provided in said hollow shaft (5). Router according to one of the preceding claims, characterized in that said means for releasing said tang (14) from said seat (13) include a jack (34) the stem (36) whereof acts axially on said bolt (27). Router according to claim 6, characterized in that said sensor means (40) are adapted to detect the position of said bolt (27), and in that it comprises further sensors means (41) adapted to detect the axial position of said stem (36) and to put the router into its halted condition during tool replacement. Router according to one or more of the preceding claims, characterized in that said stay bolt (27) and said stem (36) are axially crossed by respective channels (44, 45) which are mutually connectable upon lifting of said stem (36), with one of the channels (45) being further connectable, during tool replacement, to a source of compressed air, said channels (44, 45) forming said means for supplying compressed air to said conical seat (13). Method for tool replacement in a router for carpentry according to claim 1, comprising the steps of: actuating the tool releasing means (34) so as to act on the tang retaining means (23, 24, 27) for releasing the tool tapered tang (14) from the conical seat (13); actuating the tool expelling pin (26) to abut on the free end of said tool tang (14) for the expulsion thereof out of said seat (13), characterized in that it further comprises the steps of supplying compressed air at said conical seat (13) during the expulsion step of said tool tang (14) so as to clean the seat; external venting of the compressed air which is indicative that a tool changing operation is in course; and, after insertion of a new tool tang in said seat (13), detecting by way of the sensors (40,41) the axial position of said stay bolt (27) and stem (36).

Inventors: GEMMANI GIUSEPPE, GEMMANI, GIUSEPPE
Applicants: SCM GROUP SPA, SCM GROUP S.P.A.
Application year: 1994
Main classification: B23B31
IPC codes: B23B31, B27C5